安装NLTK之前，先用一下apt-cache search命令搜索一下NLTK包在软件源中具体的名字：
$ apt-cache search nltk #搜索软件包
python-nltk – Python libraries for natural language processing
$ apt-cache show python-nltk #显示版本信息/大小等
Package: python-nltkPriority: optionalSection: universe/pythonInstalled-Size: 4042Maintainer: Ubuntu Developers <ubuntu-devel-discuss@lists.ubuntu.com>Original-Maintainer: Robin Munn <robin_munn@sil.org>Architecture: allSource: nltkVersion: 2.0~b9-0ubuntu3Depends: python2.7, python (>= 2.7.1-0ubuntu2), python (<< 2.8), python-yamlSuggests: python-numpy, python-matplotlib, prover9Filename: pool/universe/n/nltk/python-nltk_2.0~b9-0ubuntu3_all.debSize: 918844Bugs: https://bugs.launchpad.net/ubuntu/+filebugOrigin: Ubuntu注意一下Depends/Suggests两项。或者用以下命令：
$ apt-cache depends python-nltk #了解具体依赖的包
python-nltk依赖: python2.7依赖: python依赖: python依赖: python-yaml建议: python-numpy建议: python-matplotlib建议: prover9
了解的差不多了，开始安装：
$ sudo apt-get install python-nltk #安装nltk
将会安装下列额外的软件包：libyaml-0-2 python-yaml建议安装的软件包：python-numpy python-matplotlib prover9下列【新】软件包将被安装：libyaml-0-2 python-nltk python-yaml
为了避免出现别的问题，，就把建议的包全部装上呗：
$ sudo apt-get install python-numpy
将会安装下列额外的软件包：
libblas3gf libgfortran3 liblapack3gf建议安装的软件包：python-numpy-doc python-numpy-dbg python-nose python-dev gfortran下列【新】软件包将被安装：libblas3gf libgfortran3 liblapack3gf python-numpy
$ sudo apt-get install python-matplotlib #画图表要用的
将会安装下列额外的软件包：python-matplotlib-data python-pyparsing python-support python-tz ttf-lyx建议安装的软件包：dvipng ipython python-configobj python-excelerator python-matplotlib-docpython-qt3 python-qt4 python-scipy python-traits python-wxgtk2.8texlive-extra-utils texlive-latex-extra下列【新】软件包将被安装：python-matplotlib python-matplotlib-data python-pyparsing python-supportpython-tz ttf-lyx
$ sudo apt-get install prover9
将会安装下列额外的软件包：libladr4建议安装的软件包：ladr4-apps prover9-doc下列【新】软件包将被安装：libladr4 prover9
$ sudo apt-get install python-scipy #俺跑MaxentClassifier要用的
将会安装下列额外的软件包：g++ g++-4.6 libamd2.2.0 libexpat1-dev libssl-dev libssl-doclibstdc++6-4.6-dev libumfpack5.4.0 python-dev python2.7-dev zlib1g-dev建议安装的软件包：g++-multilib g++-4.6-multilib gcc-4.6-doc libstdc++6-4.6-dbglibstdc++6-4.6-doc下列【新】软件包将被安装：g++ g++-4.6 libamd2.2.0 libexpat1-dev libssl-dev libssl-doclibstdc++6-4.6-dev libumfpack5.4.0 python-dev python-scipy python2.7-devzlib1g-dev好了，安装完毕。打开Python交互环境，import一下，看是否安装成功。
附：
https://launchpad.net/ubuntu/+source/nltk
此网站可下载到以上所有的deb安装包。
就会犯错误，就会有无数次让自己跌倒的机会出现，
